Portion of a seat



FIG. 1 is a perspective view of the ornamental design of a portion of a seat; and,

FIG. 2 is a front view of the portion of a seat.

The broken line showing of the environment is for illustrative purposes only and forms no part of the claimed design. The broken lines which define the stitching pattern of the seat form no part of the claimed design. The top, bottom, and both side views are not part of the claimed design. 

We claim the ornamental design for a portion of a seat, as shown and described. 